Northwest University of Science and Technology (2011)

Halaxylon Ammodendron Population Dynamics and Sustainable Development in Gurbantunggut Desert

宋于洋； Song Yu Yang

Titre : Halaxylon Ammodendron Population Dynamics and Sustainable Development in Gurbantunggut Desert

Auteur : 宋于洋； Song Yu Yang

Grade : Doctoral Dissertation 2011

Université : Northwest University of Science and Technology

Résumé partiel In this paper, H.ammodendron population in the Gurbantunggut Desert was taken as the research object by plot investigation and anchor point measure in the different regions. Soil seeds bank, seedling establishment, spatial pattern and dynamic characteristic were studied ; establishing age function, opening out the fecundity, reproductive value and RA ; discussing effect of coverage and species richness of community to dune stability, in order to to provide theoretical bases for protecting and utilizing H.ammodendron population. The main results were as follows :(1) The pattern of soil seeds bank in H.ammodendron:On the vertical distributions, seeds of H.ammodendron were concentrated distribution in Ocm-lcm soil layer. Soil seed density decreased rapidly with soil depth. Analysis of isotropic spatial structure of soil seeds bank showed that there were significant differences in spatial pattern strength and spatial structure composition among different plots, besides the partial plot, all other plots showed spatial autocorrelation, the scale of spatial autocorrelation were between 5 and 44.449m. The anisotropy of spatial pattern of H.ammodendron seeds bank mainly reflected on 0°(or 90°)and 45°(orl35°). The spatial heterogeneity of each plot can be showed quite well in 5m or a smaller interval distance. There was significantly correlation between seeds bank and vegetation coverage, soil water content etc.(2) Seedlings establishment:Seedlings of H.ammodendron within 2 to 4 years old and 5 to 6 years old appeared around adult, the downfold of the windard slope or crack of interdune. The site with the largest number of seedling was windward slope, next came interdune, lee slope and crest. Terrain and coverage occupied a dominant position in influencing factors of establishment. Next to soil moisture, soil salt content. The suitable region of establishment was appropriate slope, highter coverage and better soil condition.(3) The dynamic characteristics of H. ammodendron:the survival curve of H. ammodendron populations tended to be the type of Deevey-III, the mortality rate of H. ammodendron was high at early stage and low at late stage, there existed 2-4 death peak phases in the population life process. Upscaling process of spectral in different habitat shows that the change in small scale was more prominent, and was steady in large scale. So, the area of H. ammodendron Population fluctuation in the Gurbantunggut Desert was 8000-9200 m2 in suitable region,11600-14000 m2 in the region of poor condition.(4) In L(r) function (the derivation of Ripley’s K(r) function), aggregated distribution is the main trend as a whole and the scale ranges from 0m to 25m, while in g(r) function the case is similar within 5 meter s scale. Both the L(r) function and g(r) function show that with the development of the H.ammodendron from seedling and sapling into the adult, the distribution trend changes from aggregated to stochastic or uniform distribution in some scale. As to the spatial correlationship, positive correlation is shown in both the L(r) and the g(r) functions, but the scale is larger in L(r) function than that in g(r) function. In L(r) function the relationship between seedling and sapling or the grown tree is positive within 18m’s scale, while in g(r) function positive correlation is shown between the seedling and the sapling within 5m’s scale, whereas negative correlation is shown between the sapling and the adult within 8m’s scale.